Well, The test started out well…..but then…

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    drifter

    US Member - 1 Year
    Replies: 144
    Topics: 92
    #198699

    A few weeks ago I posted about a pending swap in lower cases on a 1945 Evinrude 7.5hp. I was swapping the lower cases from a 1957 Evinrude 5.5 into the 7.5.. I took many measurements and all seemed fine. I proceeded with the rebuild. New lower unit seal kit, new upper drive shaft seals, new impeller, etc..All went together just fine with nothing out of the ordinary showing up. Everything turned very smoothly and shifted fine on the bench.
    Today was test tank day. Motor started fine and dialed in fine. Water pumped great amounts. Engine shifted fine in F-N-R. After about 15 minutes of picture taking and tuning I noticed very little water being pumped. then I noticed that when shifting into F or R, the engine would immediately die. A little more fiddling and water was intermittent and engine was getting warm and would always immediately die when shifted.
    So, nothing to do but to pull the power head and investigate. With the power head off, I could barley turn the drive shaft using an old crankshaft. Really, really tight! A shock absorber I thought, but how could that be when it was fine (yes, I measured it during the rebuild to 6 11/16″) when I did the rebuild and this engine only ran in the test tank today. The shock was indeed broken and had expanded 1/4″. It expanded enough to warp the bearing housing damaging it beyond usefulness. The impeller looked fine as did the impeller housing. Also, and this is a big also, the l/u had a lot of water in the oil, with everything being covered in milky oil. When installing the seal kit, everything was normal.
    So, I’m confused. How could the shock absorber break? Maybe just age? Why did the water flow stop, (actually it would come and go but nothing close to the flow when the motor first ran). Why was there so much water in the l/u oil?
    Thanks for your help and I am eager to find some answers. I will have the shock welded since I use brass shear pins.
    Drfter

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    gjonz

    US Member - 1 Year
    Replies: 178
    Topics: 16
    #198706

    Those shock absorbers are a pest. I ALWAYS weld them and use a soft shear pin. Talk about reinventing a better mouse trap!

    Either way when the seal housing on the driveshaft was broken that causes loss of vacuum and thus water pumping would decrease. Also water can now get into the gear case a mix with the 90 wt oil causing a milkshake.

    Alternatively you could just be seeing fuel/oil/ water mix in the water from the exhaust. Depends how much.

    Barrels have nowhere to get rid of that mixture so it usually looks worse than it is.

    Greg

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    jp53-n

    US Member - 2 Years
    Replies: 36
    Topics: 11
    #198709

    Greg, where do you weld the shock absorber? I had a similar failure on a 55 5.5 and I replaced the shock absorber, but didn’t think to weld the replacement. BTW The original one failed in the test tank while tuning in gear!

    labrador-guy
    labrador-guy

    US Member - 2 Years
    Replies: 341
    Topics: 37
    #198731

    Drifter, man I hate it when that happens! Like yogi used to say “dejavu all over again”! I hate to admit it but I had one of those 5 1/2 apart three times and it set all apart for over a year before I figured it out. I always weld the shock thingy now. I will post a picture for you to see what to do.

    dale

    IMG_0002-001

    Weld or tack it so it doesn’t climb up on the coil and get longer!

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    aquasonic

    US Member - 2 Years
    Replies: 379
    Topics: 32
    #198739

    Pinion shaft shock absorbers can and do break in test tanks. I have a 54′ Johnson CD that broke two shocks just running them in a tank. All it took was shifting the motor into gear. Both shocks had saltwater use, however.

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    drifter

    US Member - 1 Year
    Replies: 144
    Topics: 92
    #198742

    I guess that I was due. I have run dozens and dozens in my tank and never had a problem. I am still confused as to why the water pumping issue came up. The bearing housing was deformed but not broken. The l/u oil was badly water contaminated. I have never had these issues come up like this. Do you think running with the water intake plate in place in the tank is an issue? I have always left it in place but read in an owners manual to remove it when running in a tank.

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    Steve Martin

    US Member - 1 Year
    Replies: 41
    Topics: 10
    #198743

    I have one that needs to be welded. Is the correct length 6 11/16?

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    drifter

    US Member - 1 Year
    Replies: 144
    Topics: 92
    #198744

    Yes. Some say 6 3/4″ but all of mine measure 6 11/16″. Probably splitting hairs on this.

    oldemtr
    oldemtr

    US Member - 1 Year
    Replies: 64
    Topics: 8
    #198745

    Hmmm – A timely thread .
    I have a 5.5 I have apart now.
    Although the motor doesn’t seem to have the expanded shock absorber issue, at present, I’m thinking to pull it out and weld, to eliminate future problems.
    Some would say that if it ain’t broke don’t fix it, but I’d hate to find out about this, some day, far up the river ……
    I have bronze shear pin stock in a couple sizes, that I put in all the motors anyway, and I have no problem with replacing them “in the field”.

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    drifter

    US Member - 1 Year
    Replies: 144
    Topics: 92
    #198746

    I know very little about welding. Should these parts be TIG welded? I have paid to have it done in the past but boy, they charged me a ton for it.

    oldemtr
    oldemtr

    US Member - 1 Year
    Replies: 64
    Topics: 8
    #198749

    The part is steel, I believe, so mig welding is probably fine.
    I’d think a couple good penetration tack welds, evenly spaced around it, should work – At least, that’s what I plan :~)

    OMC Pinion Shaft Shock Absorber

    7th post down, tells how to do it.

    • This reply was modified 2 months ago by oldemtroldemtr.
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    gjonz

    US Member - 1 Year
    Replies: 178
    Topics: 16
    #198758

    Just tack weld it is fine.

    What happens is the spring when broken acts like a ramp and one end of the spring tides UP over the other and causes the cylinder to grow. Then it will usually crack the seal housing above is. So…if it’s deformed I’d venture a guess it is cracked.

    With that said is will weld the shock absorber or there is plenty of meat on that bearing housing to shave some off the lower part of the bushing to allow for sudden expansion if the spring gives. Just use a file or sander and remove an 1/8 of an inch if you want to use the shock as intended.

    But given the oversized spring in that cylinder, it will eventually give to fatigue.

    Greg.

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    stanley

    US Member - 1 Year
    Replies: 397
    Topics: 103
    #198785

    What OMC models had the troublesome shock absorber?Also,is it “shock”or metal fatigue that causes them to break?

    • This reply was modified 2 months ago by Avatarstanley.
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    fleetwin

    US Member - 2 Years
    Replies: 3044
    Topics: 42
    #198801

    I guess that I was due. I have run dozens and dozens in my tank and never had a problem. I am still confused as to why the water pumping issue came up. The bearing housing was deformed but not broken. The l/u oil was badly water contaminated. I have never had these issues come up like this. Do you think running with the water intake plate in place in the tank is an issue? I have always left it in place but read in an owners manual to remove it when running in a tank.

    Are you sure the upper seal bushing housing is not cracked? Usually, this housing gets cracked when the driveshaft expands pushing up on the bushing housing…Once the housing is cracked, water enters the gearcase which would explain your milky gear lube. Is there signs of oil inside the impeller housing?
    On the other hand, the milky gear lube might just be a coincidence, perhaps the gearcase has a different leakage issue not related to a crack in the housing….

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    drifter

    US Member - 1 Year
    Replies: 144
    Topics: 92
    #198828

    Fleetwin, I cannot see any crack, and I looked with a strong magnifier. The deformity was barely visible and I worked flat with a brass 3/8″ drift. I checked everything with a flat steel 6″ ruler.
    I didn’t see any lube in the impeller housing. The l/u had a brand new seal kit in it. (But, new doesn’t always mean good).

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